Tire construction



July 23, .1946. w. s. COBEN 2,404,579

TIRE CONSTRUCTION Filed Oct. 21, 1941 2 Sheets-Sheet 1 v INVENTOR william 5. 60km v ATTORNEYS July 23, 1 946. w s (:QBEN 2,404,579

TIRE CONSTRUCTION Filed Oct. 21', 194-1 2 Sheets-Sheet 2 INVENTOR 101mm 5. Qo'ben ATTORNEYS shoulders thereof.

Patented July 23, 1946 TIRE CONS TRUGTION William S. Cohen, Akron, Ohio, assignor to. The Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ohio Application October 21, 1941, Serial No. 415,851

This invention relates to tire constructions, and more especially it relates to improved design of the tread portions of pneumatic tire casings. The invention has been found to be of. primary utility in its application to large heavy duty tires, such as truck tires, which are subject to relatively heavy loads and severe service conditions.

The chief objects of the invention are to improve the wearing qualities of pneumatic tires; to improve the traction and anti-skid characteristics thereof; and to provide a tire tread that has a cooling eiTect on a tire at the hinge-points thereof. Other objects will be manifest as the description proceeds.

Of the accompanying drawings:

Fig. 1 is a perspective view of a pneumatic tire casing embodying the invention;

Fig. 2 is a section, on a larger scale, on the line 22 of Fig. 1;

Fig. 3 is a section, on a larger scale, on the line 3-3 of Fig. 1;

Fig. 4 is a section on the line 44 of Fig. 2;

Fig. 5 is a section on the line 5--5 of Fig. 2; and

Fig. 6 is a fragmentary developed plan view, on a larger scale, of the tread portion of the tire shown in Fig. 1.

Referring to the drawings, there is shown a tire comprising the usual carcass l of a plurality of fabric plies, dual bead cores H, H at each margin of said carcass, as is conventional practice in heavy duty tire construction, and a tread structure, designated as a whole by the numeral l2, on the periphery of the said carcass.

1 Claim. (01. 152-409) Said tread structure is formed with a plurality of circumferentially extending driving or traction elements which for convenience may be designated as central, intermediate, and lateral elements, said elements being separated b circumferentially extending grooves I3, I3.

The central traction element is a rib l5 that is symmetrically disposed along the centerline of the tread, equidistant from the lateral margins 01 The respective lateral faces of the rib 5 are serrated, that is, they are formed with a succession of lugs IS, IS that are wedge shape in plan, and which project into the grooves |3 at opposite sides of the rib. The lugs I6 on one side of the rib are disposed in staggered rela tion to the lugs on the other side of the rib, as is most clearly shown in Fig. 6.

The intermediate traction elements are circumferential ribs l8, l8 that are disposed adjacent the rib |5 on opposite sides thereof. The ribs 8 as shown are identical with the rib l5 except in one important feature, namely, they '21 are somewhat narrower than said rib I5; 'Like the latter, the lateral faces of the ribs l8 are serrated, the lugs that constitute the serrations being designated L9, l9. The lugs IS on opposite sides of each rib I8 are in staggered relation to each other, and on that side of each rib l8 that is nearest the rib IS, the lugs l9 are in staggered relation to the lugs [6 of the said rib l5. The arrangement is such that the grooves [3 between the rib l5 and ribs |8 has a zig-zag appearance.

The lateral traction elements are disposed at the respective margins of the tread, which are the shoulders or hinge points of the tire. Each of said lateral traction elements consists of a circumferential series of blocks 2|, 2| that are longitudinally spaced apart from each other, said blocks being of greater length than width and being disposed end to end.

The lateral face of each block 2| that confronts an intermediate rib I8 is serrated, the wedge-shaped lugs that constitute the serrations being designated22. The lugs 22 are disposed in staggered relation to the lugs I9 of the adjacent rib l8 so that the intervening groove I3 is of zigzag appearance. The opposite face of each block 2| is sloped from the circumferentially arranged margin of the block to the sidewall of the tire. A characteristic feature of the lateral traction elements is their transverse width, which width is less than the width of the intermediate elements IS on the ground-engaging surface of the elements. It will also be observed that the blocks 2| on one side of the tread are staggered with relation to the blocks 2| on the opposite side of the tread. Adjacent blocks 2| of each series are connected to each other by ribs 23 that are integral therewith, said ribs being of narrower width than the blocks, and being somewhat lower in height, as is best shown in Fig. 3.

The grooves l3 that separate the traction elements are not of uniform depth throughout the circumference of the tire, but have local regions of shallower depth, which regions are spaced apart from each other a distance equal to the spacing of three of the lugs l6 or I9. The regions of shallower depth are produced by upward swells or bulges 25 in the bottom of the grooves, which swells or bulges are located at the apexes of lugs that constitute the serrations of the traction elements. The function of said bulges 25 is to impede the progress of flex cracks that may originate in the bottom of the grooves l3.

The invention provides atire having a greater proportion of its rubber at the center of its tread where service conditions are most severe, with the traction and non-skid characteristics.

points thereof where flexure produces the greatest heat.

Modification may be resorted to without .del- T parting from the spirit of the invention, or the scope thereof as defined by the' appended claim. Q

What is claimed is:

Apneumatic tire comprising a tread portion formed with a plurality of traction element's, said tractionelements comprising endless circumfer entially extending ribs in the central area of the tread and a. circumferential series of longitudinally spaced blocks disposed at the opposite lateral margins of the tread, one of said ribs being wider than the others and being disposed along the center line of the tread, all of said ribs having their lateral faces uniformly and continuously serrated throughout, said blocks being of greater length than width and having one lateral face confronting an outer rib of said tread, said confronting face of said blocks being serrated throughout their length and their other lateral faces being smooth, said blocks being connected to each other by means of a relatively narrow rib whose height is less than the height of the blocks,

said traction elements defining circumferential grooves therebetween and the bottom of said grooves having a plurality of upwardly extending bulges at intervals, said intervals being equal to the spacing of three of the said serrations whereby progressive development of a crack in the groove of the tire is prevented,- V

WILLIAM s. coBEN. 

